Distortion cancel circuit in FM stereo

Abstract

There is disclosed a distortion cancel circuit in FM stereo receiver, which circuit synthesizes a canceling signal mainly including the distortion component by performing the arithmetic operation for an FM demodulation signal and adjusts the level of this synthesized canceling signal and thereafter subtractively combining it with the FM demodulation signal. This circuit enables the elimination of harmonic distortion which appears in the stereo MPX signal output due to the band characteristic of an intermediate frequency amplifier.

I claim: 
     
       1. A distortion cancel circuit in an FM stereo receiver having an IF stage, comprising: an input terminal at which is received an FM stereo demodulation signal which contains a distortion component generated in said IF stage;   an output terminal connected to an input of an FM MPX circuit;   a circuit for synthesizing a canceling signal to eliminate said distortion component generated in said IF stage by multiplying a main signal and a subsignal of said FM stereo demodulation signal at said input terminal;   a circuit for adjusting the level of said synthesized canceling signal; and   a circuit for subtractively combining said canceling signal whose level was adjusted with said FM stereo demodulation signal.   
     
     
       2. A distortion cancel circuit according to claim 1, wherein said level adjustment circuit can change the level adjustment in accordance with the band characteristic of an intermediate frequency amplifier in said FM receiver. 
     
     
       3. A distortion cancel circuit in an FM stereo receiver having an IF stage, comprising: an input terminal at which is received an FM stereo demodulation signal which contains a distortion component generated in said IF stage;   an output terminal connected to an input of an FM MPX circuit;   a circuit for synthesizing a canceling signal to eliminate said distortion component generated in said IF stage by cubing a sub-signal of said FM stereo demodulation signal at said input terminal;   a circuit for adjusting the level of said synthesized canceling signal; and   a circuit for subtractively combining said canceling signal whose level was adjusted with said FM stereo demodulation signal.   
     
     
       4. A distortion cancel circuit accoriding to claim 3, wherein said level adjustment circuit can change the level adjustment in accordance with the band characteristic of an intermediate frequency amplifier in said FM receiver.